This invention relates to camming devices, especially of the type used in climbing applications.
Camming devices, such as those known as xe2x80x98Friendsxe2x80x99, are used to make a secure location for ropes for rock climbing. These devices are securable in cracks and the like in rock faces. A camming device generally comprises a stem carrying a transverse spindle on which are two or more, usually three or four cams that are oppositely urged to a widest extent and means for retracting the cams to a narrower extent. The known camming devices fall into three main categories, namely those that have a hooped stem and a single spindle, those that have a single stem and a single spindle and those that have a single stem and twin spindles. To use such devices, the cams are retracted, so that the cams can be pushed into a crack in a rock face and then released to grip the sides of the crack. The shaping of the cams is such that the more force is applied to pull the device out of the crack increases their grip.
There are a certain disadvantages with all such devices. Under certain conditions, there is a tendency for camming devices to xe2x80x98walkxe2x80x99 due to the effect of the forces applied to the device. The device tends to move further into the crack than originally positioned. This is undesirable, since it adds unpredictability to the holding power, especially if the device moves into a wider part of the crack. Also, the device may become irretrievable, if it walks too far to operate the trigger for retracting the cams.
A further disadvantage occurs with twin spindle camming devices. It is possible to position such devices in such a manner that the load exerted on the stem in the plane of the cams, such as for example when a climber attached to the device falls, can result in forces acting against the preferred camming action of the device and consequently compromise the holding power and safety of the device.
An object of this invention is to provide an improved camming device, especially for use in climbing applications.
According to this invention a camming device comprises a support, one or more spindles mounted on the support, at least two cam members adapted to engage the walls of a crack or hole by their cam profiles pivotally mounted on the spindle or spindles and adapted for opposite pivotal movement from a closed position to an open position, means to apply a force to each cam member to urge it to its open position, means for pivoting the cams to the closed position, characterised in that the stem includes means for movement of at least a major part thereof about an axis other than that of the or of either spindle.
In a first preferred embodiment of the invention, the camming device has one or two spindles and the or each spindle is mounted through a head of the stem, the remainder of the stem being pivotable relative to the head. Pivoting may be in a plane parallel to the cams. Alternatively, the stem may be pivotable in any direction radially of the axis of the stem. Another option is for the stem to be pivotable axially of the stem.
In a second preferred embodiment, the camming device of the invention has a single spindle and the spindle is mounted through an aperture in the stem head that is sufficiently large for limited rocking movement of the stem about the spindle, especially laterally relative to the cams. The aperture is preferably elongate along the axis of the stem. Rocking movement is preferably constrained by spring means or the like between the spindle and one end, preferably the end remote from the spindle end of the stem, of the aperture.
In a third preferred embodiment of the invention, the camming device has a stem in the form of a hoop, typically of wire and the hoop is pivotally attached at opposite sides to spindle mounts for movement parallel to the planes of the cams.
The camming devices of the present invention have in essence a greater degree of flexibility for the stem, which can reduce the tendency of camming devices to walk into cracks by taking up some or all of the forces exerted on the stem that would otherwise tend to cause walking. Alternatively or additionally side loads on stems of camming devices that can result in forces acting against the camming action may be reduced in effect.